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I am a postdoctoral researcher in the Robotics Institute
at Carnegie Mellon University working with
Prof. Nancy Pollard in the Graphics Lab. I received my PhD in Mechanical Engineering from Seoul National University, Korea in 2007, and I was advised by Prof. Frank Park in the Robotics Lab. I had also been working
for Hyundai Heavy Industries Co., Ltd.
as a researcher in the Electro-Mechanical
Research Institute from 2000 to 2005.
Research / Projects
My research is in the area of computer graphics and
robotics. I am particularly interested in physically-based motion generation
for articulated systems such as animated characters and robots. I am also
interested in developing techniques for physical simulation of the systems.
Here are the main current themes of my research:
- Interactive
Physically-Based Control of Skeleton-Driven Deformable Characters:
Imagine a fish character which happened to be on a dock and now is
trying to escape into water. There is no hand-of-God, or a mighty
external force helping it, and the only things it can rely on are its
own muscles, or actuators, and the frictional contact between its body
and the ground. In this situation, it would be very difficult to find a
good sequence of command input on the actuators resulting in an escape.
In this project, instead of developing a good motion controller or
planner, we hope to make use of the user as a motion controller,
borrowing their intuition about dynamic movements, because we believe
that people do have a good sense of how a character should move to achieve
a desired motion even for non-human characters. The goal of this project
is to develop intuitive and interactive ways to realize the user’s
intention in creating dynamic motions of skeleton-driven
 deformable body systems. Using
our approach, various interesting motions of the character can be
created by simply dragging the mouse in an intuitive way. Every motion
is generated through dynamics simulation which is guided by the
user’s control such as the mouse dragging.
- Motion
Optimization for Skeleton-Driven Deformable Characters:
Optimization-based approaches can also be applied to generate
interesting motions of animated characters. In this project we build a
mathematical framework for optimizing motions of skeleton-driven
deformable body systems which usually have lots of passive coordinates
as well as active coordinates.
- Recursive
Hybrid Dynamics Algorithm for Animated Characters: Consider a system
which has both active and passive coordinates. For example, a human
character has both kinds of coordinates, i.e., active coordinates from
its actuators, or active joints, and passive coordinates from the root
joint connecting the character to the ground. If time trajectories for
active coordinates are given and we want to obtain the resulting motion
of the whole system through dynamics simulation, then hybrid dynamics
will be a nice choice for the simulation of animated characters. Unlike
the popular forward dynamics which requires a carefully tuned servo
controller on each active coordinates, hybrid dynamics directly
considers the accelerations of the active coordinates as input command
and calculates the accelerations of the passive coordinates and the
forces acting on the active coordinates as output. The hybrid dynamics
simulation produces the very motions which would be obtained through the
forward dynamics simulation with an ideal perfect servo controller.
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